1.1 Modelling of Heat flow during Welding using ANSYS

1.1.1 Introduction

The steady state heat conduction in a moving solid can be described by the following

equation:

α∇

T − ⅆ

δT

δx

= 0

Solution of the above equation gives the following expressions for the temperature field

round a "quasi-stationary" heat source. This steady-state assumption was first used by

Rosenthal to simplify the mathematical treatment of heat flow during welding. [1]

Rosenthal’s Two-Dimensional Equation

Rosenthal used the following simplifying assumptions to derive analytical equations for heat

flow during welding:

1. steady-state heat flow

2. point heat source

3. negligible heat of fusion

4. constant thermal properties

5. no heat losses from the workpiece surface

6. no convection in the weld pool

Figure 1: Coordinate system (x, y, and z) moving with heat source. From Sindo Kou

1.1.2 Aim

In this project a heat flow simulation during welding is performed.

1.1.3 Objectives

To study temperature distribution during welding using ANSYS APDL Solver

 On Similar metals (Steel)

 On Dissimilar metals (Structural Steel + Inconel 718)

1.1.4 Geometry Preparation

Model of a rectangular slab to be welded is made in Solidworks of dimension (100x100x5)

mm.

Figure 2: Welding Specimen CAD Model

Figure 3: Welding specimens joined together

1.1.5 Meshing

A Mesh is a network that is formed of cells and points. Meshing is a part of the engineering

simulation manner where complex geometries and models are divided into simple elements

that can be used as discrete local approximations of the larger domain. The Mesh can be

resembled into any shape and size depending upon the geometry and is used to resolve

Partial Differential Equations.

[1]

Performing Meshing in ANSYS-

Load the required solver into ANSYS Workbench by drag and drop, for our project we have

selected “Transient Thermal Analysis Using Mechanical APDL Solver”.

After importing the specimen geometry Double-click on Model tab.

Figure 4: Image showing ANSYS Workbench Project Schematic page

Figure 5: Image Showing to open the Model in ANSYS Mechanical

Once the mechanical module is open we can access the mesh settings from the project tree.

Figure 6: Image Showing Mesh Settings

In this project we used tetrahedral mesh with patch conforming algorithm.

Figure 7: Image Showing Element Quality of the generated mesh

Element size is kept 2mm with 16327 elements and 30108 nodes.

Figure 8: Image Showing Magnified mesh around the edges

Mesh Metric-

Aspect Ratio-

Figure 9: Image showing Aspect ratio of the mesh generated

Skewness-

Figure 10: Image showing skewness of the generated mesh

1.1.6 Simulation Parameter Setup

For setting the simulation first we will setup the heat transfer method inside the Transient Thermal

solver hierarchy. We have chosen convection because here in case of welding convective heat

transfer is taking place.

We perform welding in controlled environment so selecting the surrounding environment as

stagnant air in the simulation.

Figure 12: Image showing selection of surrounding environment as stagnant air

Figure 11: Imaging showing location of convective heat transfer method

Now we will be parameterising the welding arc and defining the boundary conditions. We are

selecting the top faces of the specimen, edge joining the two plates and the vertex as starting point

for the welding arc.

Figure 13: Image showing the welding direction from D to C

1.1.7 Material Selection

We will be analysing two scenarios here one with similar metal and other with dissimilar metals.

Figure 14: Image showing material assignment in Project tree

Similar Welded Joints- (Steel)

Figure 15: Welding electrode is at midway in this image

Figure 16: Welding electrode has just reached the end of the vertex

Figure 17: Image showing cooling down of the slab

Dissimilar Welded Joints- (Steel + Inconel 718)

Figure 19: Image showing temperature distribution

1.1.8 Results and Conclusion

The temperature distribution are obtained in the post-processing, it is evident that temperature

increases rapidly in the beginning to around 1200 degree Celsius in the first 5 to 10 sec in

case of similar metals and temperature starts reducing as the arc reaches the end of the plate.

In the case of dissimilar metals the temperature contours are asymmetric owing to dissimilar

properties of metals. Lab Experiments needs to be supplemented for validation of the project

and other type of heat source could be analysed.

Figure 18: Image showing Temperature distribution during welding of Steel with Inconel 718

1.1.9 References

[1] Kou, S. (2021). Welding metallurgy. Wiley.

[2] G.H. Little, A.G. Kamtekar, The effect of thermal properties and welding efficiency on

transient temperatures during welding, Comput.Struct. 68 (1998) 157–165.

[3] Attarha, M. J., & Sattari-Far, I. (2011). Study on welding temperature distribution in thin

welded plates through experimental measurements and finite element simulation.

Journal of Materials Processing Technology, 211(4), 688–694.

https://doi.org/10.1016/j.jmatprotec.2010.12.003